This invention relates to a dual purpose agricultural planting implement and in particular to an implement for planting both conventionally spaced corn rows and narrow soybean rows of about one-half the corn row spacing.
Soybeans are typically planted by implements also used to plant corn. It has been found, however, that planting soybeans in narrower rows than conventional corn row spacing, provides an effective method of increasing soybean production. On-farm and university testing throughout the cornbelt region of the United States have evidenced significant yield gains with narrow rows. An initial significant move reduced soybean rows from a 40" spacing to a 30" spacing resulting in a 10-25% increase in yield. This was usually accomplished by modifying the spacing of planting units on a planter implement so that corn would also be planted in 30" rows. No change in corn yield resulted from this spacing reduction. However, more recently, studies have shown that still narrower soybeans rows will further increase yields. It now appears that the optimum row spacing for soybeans is in the range of 10-20". 15" rows have been found to give approximately a 15% yield over 30" rows except in some southern states where rows less than 15" provided even better yields.
A variety of methods of planting narrow rows of soybeans have been tried. Solid-seeding produces good yield increases but the technique has several drawbacks. For instance, weed control is a problem. Cultivation is not possible and a good weed management program is needed. This in turn requires heavy use of chemicals and a good past weed history on the field. Additionally, grain drills which are used for solid seeding have not produced very satisfactory depth control, seed placement or good seed/soil contact. A still further drawback occurs with some soils which need a cultivation which break the crust and allow areation of the soil. This is not possible with solid seeding.
There are several types of narrow-row soybean planters presently in use. The most prevalent manner of either solid seeding (6-7" rows) or very narrow row seeding (10-12") has been to plug metering holes in grain drills. A few home-made rigs have been made by farmers around the country, usually using older type planters. Commercially, there are now available specialty planters to plant just narrow row soybeans. Conventional wide-row "convertible" planters have also become available commercially to which additional planting units can be added to obtain narrow rows.
Soybeans require good planting management expecially in drier areas where spring-time moisture, specifically in the upper soil layer, is short. There must be consistent depth control, accurate seed placement and good soil/seed contact. As already pointed out, conventional grain drills are not very accurate or reliable in any of these areas. Additionally, most soybeans are grown in the cornbelt region of the United States where many farmers do not own a grain drill and cannot afford to purchase one just merely to experiment with a new soybean planting technique. Finally, the use of a drill for seeding either solid or very narrow rows, eliminates the option of cultivating and thus, puts the heavy burden of weed control upon the use of chemicals whose control depends on weather, proper timing, proper use and longevity of controls and prior field conditions. Without the option of cultivation, many producers would be forced to use expensive and sometimes ineffectual weed control.
Commercial planting units work well but are often too expensive for most farmers to afford. This is especially true for the speciality type planters which can only be used for soybeans and therefore, require the purchase of two different row planters for the typical farmer who plants both corn and soybeans. The convertible type of commercial planter, to which the extra units required can be added when needed, or left off when not needed, eliminates the requirement for purchasing two planters but can still be very expensive. The most basic planter row units, without herbicide or insecticide capability presently cost around $1000-$1200 per row. Such convertible units therefore still require a very large investment, especially for the producer who wishes to experiment for a few years with narrow-row planting to see how it suits his operation and to develop his technique. Convertible planters also require time to switch back and forth which can be very expensive during the prime planting time and cause inconvenience when filling or working on the main unit.
Typical conventional corn/soybean planters have a capability for adding herbicides during planting. However, neither the commercially available specialty narrow row soybean planters nor the existing units on commercial convertible type planters provide such herbicide capability.